You should oil your new cricket bat using linseed oil before you begin to it knock-in.
Firstly lightly sand the surfaces of the cricket bat with a fine grade of sand paper. Then apply 2-3 light coats of oil to all exposed surfaces of the bat, allowing sufficient time for the bat to dry between coats, usually overnight.
It's best to avoid oiling your cricket bat if it already has an artificial coating. Also don't stand the bat in oil as this can cause the bat to soften and be more prone to damage.
Once you have oiled your bat and it has dried out, you can then begin to knock-in your new cricket bat, click here for tips on knocking in a new cricket bat .
After a match always check over your bat for signs of damage, such as cracking or splitting of the wood. You can repair damage by sanding and cleaning the damaged area, then using super glue or cricket bat tape to repair any small surface cracks.
During the off season, avoid storing your new cricket bat in a dry/warm location. Particularly avoid storing your bat in direct sunlight or rooms in your house where there are artificially high temperatures, as this will cause the bat to dry out.
At the end of the season if is often worth applying another light coat of linseed oil and again at the start of the next season. But don't over oil as you may end up weakening the willow.
If you take good care of your cricket bat it should easily last at least 3-4 seasons. However if you mistreat it and don't care for it, it will be much more prone to damage. It is normal however to get surface cracks on any cricket bat, even new bats, these are easily repaired with tape or glue and shouldn't affect the quality of the bat.
But if a major split does occur it's worth contacting your supplier, as they may send it back to the manufacturer, who will often repair it or send you a new one. However if it is clear the bat has been mistreated, it's unlikely they will repair or replace it.